Question

Magnetic field at a distance $r$ from an infinitely long straight conductor carrying a steady current varies as

• A. $\frac{1}{r^2}$
• B. $\frac{1}{r}$
• C. $\frac{1}{r^3}$
• D. $\frac{1}{\sqrt{r}}$

Answer 1

The correct option is B $\frac{1}{r}$

Magnetic field at a distance $r$ due to an infinitely long straight conductor is given by-

$B=\frac{{\mu }_{o}I}{2\pi r}$

$⟹$ $B\propto \frac{1}{r}$